Abstract
Bunches in the Tevatron are known to exhibit longitudinal oscillations which persist indefinitely. These oscillations are colloquially called 'dancing bunches.' Although the dancing proton bunches do not cause single bunch emittance growth or beam loss at injection, they lead to bunch lengthening at collisions. In Tevatron operations, a longitudinal damper has been built which stops this dance and damps out coupled bunch modes. Recent theoretical work predicts that the dance can also be stopped by an appropriate change in the bunch distribution. This paper describes the Tevatron experiments which support this theory.
Highlights
Since the start of Run II, the proton bunches in the Tevatron have been observed to have longitudinal oscillations which persist indefinitely
The reason for the persistence of these oscillations has been traced to the loss of Landau damping (LLD) caused by the inductive impedance of the Tevatron [3]; these oscillations are colloquially called ‘‘dancing bunches.’’ At the injection energy of 150 GeV, these oscillations do not seem to cause any emittance growth or any beam loss
In the KEK-PS and SPS, the rf perturbation is applied to the voltage amplitude while at the KEK Photon Factory, noise is applied to the rf phase
Summary
Since the start of Run II, the proton bunches in the Tevatron have been observed to have longitudinal oscillations which persist indefinitely. The initiators of these oscillations for coalesced [1] bunches come from the coalescing process (see Sec. III A 2) and possibly from injection errors [2]. The reason for the persistence of these oscillations has been traced to the loss of Landau damping (LLD) caused by the inductive impedance of the Tevatron [3]; these oscillations are colloquially called ‘‘dancing bunches.’’ At the injection energy of 150 GeV, these oscillations do not seem to cause any emittance growth or any beam loss. The goal of this paper is to demonstrate experimentally that the dance can be stopped by changing the beam distribution appropriately
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